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FullRangeMan 27th February 2011 10:12 PM

Toroidal Output Transformer
 
Hi,
I always saw few SETs with Toroidal Output Transformers, most use laminated trafos.
Why this happen??
Toroidal are more expensive??
Or Laminated offer better sound quality??

Need your opinion to know what is the better choice, Toroidal or Laminated for a 6C33 SET, 15Watts/8 ohms, I will use 8 ohms tap only.
I accept suggestions of both cores you may know.
Any help will be appreciated.
Gustavo

pieter t 27th February 2011 10:28 PM

Gustavo,

Searching this forum you will find much info on toroidal, EI and c-core output transformers.
In my opinion and experience the c-core transformer is the best option, but once more, look around here.

LinuksGuru 27th February 2011 10:52 PM

For SET - anything but not not toroidal. Fixed air gap toroids are too problematic to make. Distributed air gap cores are made for chokes, not audio transformers.

pieter t 27th February 2011 11:05 PM

LinuksGuru,

Despite my preference for c-cores I am not so sure that "all toroidals are the same and therefore not good for SE".
I know that toroidal cores are not only available as uncut closed loops but also in cut halves (like c-cores). Applying appropriate airgaps should not be too much of a problem with cut toroids.

LinuksGuru 27th February 2011 11:33 PM

Quote:

Originally Posted by pieter t (Post 2485531)
LinuksGuru,

Despite my preference for c-cores I am not so sure that "all toroidals are the same and therefore not good for SE".
I know that toroidal cores are not only available as uncut closed loops but also in cut halves (like c-cores). Applying appropriate airgaps should not be too much of a problem with cut toroids.

I know no factory in Europe capable to make assembled units of cut (fixed air gap) toroids (only seen some in China).
Technically even at home its possible to use band saw to cut them in halves, and then glue with epoxy and tiny piece of mylar film in between to make air gap, but this is kinda awkward.

Water or laser cutting machines capable to work with so thick piece of metal possibly available somewhere but I'm not sure.

EI/double C cores are more suitable to make precision air gap, no reasons to mess with toroids for SET.

tinitus 27th February 2011 11:55 PM

Quote:

Originally Posted by LinuksGuru (Post 2485555)

Water or laser cutting machines capable to work with so thick piece of metal possibly available somewhere but I'm not sure.

'piece of cake' ;)

why not cut a bundle of 'half moons' of transformer iron sheet
make two half moon plastic bobbins for the winding

when forming a perfect circle, they should all slide very easily into each other, and voila, a toroidal double C-core

pieter t 28th February 2011 08:53 AM

Quote:

Originally Posted by tinitus (Post 2485572)
'piece of cake' ;)

why not cut a bundle of 'half moons' of transformer iron sheet
make two half moon plastic bobbins for the winding

when forming a perfect circle, they should all slide very easily into each other, and voila, a toroidal double C-core

Maybe possible mechanically, but makes no sense at all.
What is to gain with this?
Good quality c-cores are annealed after forming; bending iron to form a core without annealing will impair the quality.
At the end I see no advantage in winding a circular core (with all possible haphazardness) over winding a neat straight coil for a c-core.
Quite a lot on this subject has been discussed in other threads.

tinitus 28th February 2011 11:49 PM

1 Attachment(s)
Quote:

Originally Posted by pieter t (Post 2485925)

bending iron to form a core without annealing will impair the quality.

not bending, or rolled
stacked iron
with plastic bobbin
like the ususal
just different, toroid style

I dont know if theres any advantage, no clew, nada
nor do I know what kind of winding machine needed
but with bobbin, open winding should be possible, and different from regular toroid

but one major problem
I guess no parts available anywhere
but hey, this is DIY, right ?

FullRangeMan 1st March 2011 02:15 AM

Hi,
Thanks for your comments. I thought the best sound was clearly known.
If the best sound is uncertain I would like to read your technical considerations on the subject.
Thanks a lot,
Gustavo

tinitus 1st March 2011 02:21 AM

Quote:

Originally Posted by FullRangeMan (Post 2485472)
Hi,

Need your opinion to know what is the better choice, Toroidal or Laminated for a 6C33 SET, 15Watts/8 ohms, I will use 8 ohms tap only.

I accept suggestions of both cores you may know.
Any help will be appreciated.
Gustavo

oh, lead astray, sorry
never forget to read the first post, eh
well I forgot :o

I would say C-core, surely

but C-core aint just C-core, they may be different too

but there could be more to it than just choosing core type
like production quality, winding design, impregnating, etc

whatever, I have heard pretty crappy sound from amp using top quality trafo
and I dont doubt its possible to get real good sound from budget quality components, trafos included


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